The laser beam is well known for high collimation, high power and high light intensity, so that the laser beam apparatus has very wide applications in modern industries, such as highly-collimated light source in laboratory, laser pen used to point at screen of a briefing, laser light source adopted in reading or burning disks, laser light source adopted by a mouse, laser light sources for a variety of measuring instruments, laser light source in display field, laser light source in optic fibber communications, even laser light source for the instruments in the biomedical field.
Since the laser beam emitted by a laser beam has high coherence and therefore, when the laser beam irradiates a non-smooth surface of an object (such as lenses, reflectors, etc.), the laser beam reflected from the object surface produces interference and speckles on the irradiated surface. Speckles are irregular noise-like pattern (for example, irregular bright and dark messy spots), it will result in non-uniform illumination on the irradiated surface to degrade the optical quality of the apparatus employing the laser light source.